How to access a checkbox in a table?

Question

PyQt

I'm making an application, as planned, a table is generated from the data received via REST. I make a checkbox the first cell of each row. I hang on each checkbox the function of recalculating the total amount of one of the columns. By design, the function should go through all the rows and summarize only the cells of those rows where the checkbox is checked.
The question is how do I get the state of the checkbox when iterating over the rows?
This is how I generate the table content:

table = self.ui.historyTable
for i, op in enumerate(totalop):
            self.checkbox = QtWidgets.QCheckBox()
            self.checkbox.setCheckState(QtCore.Qt.CheckState.Checked)
            self.checkbox.setStyleSheet('margin-left:12px;')
            self.checkbox.stateChanged.connect(self.recalc)
            table.setCellWidget(i, 0, self.checkbox)
            table.setItem(i, 1, QtWidgets.QTableWidgetItem(ticker)
            table.setItem(i, 2, QtWidgets.QTableWidgetItem(op.get('operationType')))
            table.setItem(i, 3, QtWidgets.QTableWidgetItem(str(op.get('price')).replace('.', ',')))

Well, I'm trying to process a click on the checkbox:

def recalc(self):
        table = self.ui.historyTable
        for i in range(table.rowCount()):
            item = table.item(i, 0)
            # ???

However, in item I have None. Tell me how to get access to the checkbox to read the status from it.